The overall goal of the proposed work is to better understand the covert movement-related activity that accompanies imagined actions. The proposed experiments will monitor the activity or three movement- related areas of the cerebral cortex - primary motor cortex (Ml), premotor cortex (PM), and the supplementary motor area (SMA) - during real and imagined movements. To do so, they will employ scalp recordings of event-related brain potentials. These measures have sufficient temporal resolution to detect changes in brain activation that occur on the order of milliseconds and, thanks to recent developments, can now be used to monitor each of the above cortical areas individually. The experiments will monitor Ml, PM, and SMA, under some of the main conditions in which covert movement has been proposed to take place. These include mental practice (as in sports or music), observation prior to imitation (as in skill learning), memory rehearsal of movements, and the phantom limbs of amputees. The overt and covert movements to be studied will include, rhythmic sequences of taps made with the hands or feet, sequences of signs from American Sign Language, and "movements" of a phantom limb. Information about the presence and precise timing of covert movement-related activity in MI, PM, and SMA could have a number of applications. Such information might 1) predict the efficiency of mental practice, observational learning, or clinical treatment to aid motor recovery; 2) serve as the basis for feedback; 3) help diagnose disorders of the motor system; or 4) help determine the direct consequences of covert movement-related activity in the studied brain areas for learning, remembering, and fine tuning overt movement. At a broader level, the proposed work is likely to enhance our understanding of the motor system at both a psychological and physiological level; Further information concerning its less-known covert side may lead to unexpected insights about movement in general.